Field of the Invention
The present invention relates generally to video playback and, more specifically, to real-time scrubbing of videos using a two-dimensional grid of thumbnail images.
Description of the Related Art
Manually searching for a specific location in a digital video file by “scrubbing,” i.e., by moving a cursor along a timeline slider associated with the video, can be performed fairly conveniently with a downloaded video. This is because the current selected frame of the downloaded video can generally be accessed and displayed almost immediately after the cursor is positioned at any point on the timeline slider. This allows a viewer to quickly determine what portion of the video corresponds to the current cursor position and whether the cursor should be repositioned to find the target location in the video. However, due to the long wait time associated with downloading longer videos before viewing of the video can begin, video streaming has become a popular alternative to video downloading.
Streaming video, in which audio-visual media are constantly received and presented to an end-user while being delivered by a provider, allows viewing to begin after a relatively short period of data buffering has taken place. This is because the bulk of the downloading process takes place while the video is being presented to the end-user. However, in contrast to downloaded videos, which are fully cached, searching for a specific location in a streaming video can be problematic. Specifically, when an end-user searches for a specific location in a streaming video by scrubbing a cursor position forward or backward along a timeline associated with the video, the end-user must wait for the data buffering process to complete before the portion of the video corresponding to the current cursor location is displayed. This is because streaming video players are generally unable to display video frames until a certain level of buffering has taken place. Unfortunately, such display latency occurs each time the cursor is repositioned, even if the cursor is only repositioned a very short distance along the video time line. Because the cursor is generally repositioned many times in the course of navigating to a target location in a video, even when the requisite data buffering takes as little as a few seconds, navigation performance is significantly degraded. Thus, such display latency can make the video scrubbing experience for the end-user very choppy, time-consuming, and frustrating.
Recent techniques to improve real-time seeking in a streaming video include displaying one or more pre-cached thumbnail images during seeking that correspond to the current seek location in the streaming video. Displaying thumbnail images while a viewer scrubs to a desired location in a streaming video can assist the viewer in navigating to the desired location and thereby address the latency issues described above. However, such techniques break down for longer streaming videos, for example full-length movies, since scrubbing a timeline generally results in each individual pre-cached thumbnail image being displayed too quickly to be comprehensible and assist in navigation. Furthermore, shorter scenes in a long streaming video, for example scenes that are one or two minutes, can be so short that there is no pre-cached thumbnail image to be presented, thereby making navigation to such a scene using thumbnail images problematic.
As the foregoing illustrates, there is a need in the art for a more effective way to navigate videos.